1. Field of the Invention
The present invention relates to a light emitter substrate which is applied to a face plate of an electron beam displaying apparatus, and an image displaying apparatus which is constituted by using the light emitter substrate.
2. Description of the Related Art
In recent years, a flat panel image displaying apparatus in which an electron source substrate on which a number of electron-emitting devices are arranged and a light emitter substrate on which plural light emitter layers emitting light in response to irradiation of electrons emitted from the electron-emitting devices are arranged are opposed to each other has been developed as a next-generation image displaying apparatus. Although there are different kinds of electron-emitting devices, these devices basically use field emission. Therefore, such a displaying apparatus which uses these electron-emitting devices is generally called an FED (field emission display). In the various FEDs, the displaying apparatus which uses surface conduction electron-emitting devices is specifically called an SED (a surface-conduction electron-emitter display). However, in the present application, the term FED is used as the generic term which includes the SED.
The FED has the electron source substrate (i.e., a rear plate) and the light emitter substrate (i.e., a face plate) which are oppositely arranged at a narrow gap of approximately 1 mm to 2 mm. These substrates constitute a vacuum envelop by mutually bonding the respective peripheral portions thereof through a rectangle-frame side wall. A degree of vacuum of the inside of the vacuum envelope is maintained at high vacuum of approximately 10−4 Pa or less.
On the inner surface of the electron source substrate, a large number of electron-emitting devices for emitting electrons are provided, a large number of scanning lines and signal lines are formed in matrix, and the scanning line and the signal line are connected to each of the electron-emitting devices. On the inner surface of the light emitter substrate, R (red), G (green) and B (blue) phosphors are formed as a light emitter layer, and an anode voltage is applied to the formed phosphors. If electron beams emitted from the electron-emitting devices and accelerated by the anode voltage collide with the phosphors, the phosphors emit light, whereby an image is displayed. Further, a rib is provided between the phosphors so as to prevent that a part of incident electrons is reflected on the arbitrary phosphor and the reflected electrons enter into the phosphor adjacent to the arbitrary phosphor.
In order to obtain a practical displaying characteristic in the FED constituted as described above, the phosphors which are the same as those in an ordinary cathode ray tube are used, and further an aluminum thin film called a metal back is formed on the phosphors. In this case, it is desirable that the anode voltage to be applied to the metal back is set to several kilovolts at the lowest, preferably to 10 kV or higher.
However, the gap between the light emitter substrate and the electron source substrate cannot be so enlarged from the aspect of resolution, a characteristic of a spacer, and the like. More specifically, it is necessary to set the relevant gap to approximately 1 mm to 2 mm. Therefore, in the FED, it is impossible to avoid generating a high electric field at the above-described small gap between the light emitter substrate and the electron source substrate, whereby a problem of a discharge between these substrates generates.
If any countermeasure is not introduced to suppress damage by the discharge, the electron-emitting device, the phosphor, a driver IC, a driving circuit and the like are damaged and/or deteriorated due to the discharge. Here, it is assumed that such damages and deteriorations are collectively called discharge damage hereinafter. Under the circumstance that the discharge damage occurs, it is necessary to absolutely prevent the discharge from generating over the long term so as to put the FED to practical use. However, it is extremely difficult to achieve such a countermeasure.
Consequently, a countermeasure for reducing, even if the discharge generates, a discharge current is important so as to be able to suppress the discharge to the level that the discharge damage does not occur or can be ignored. To achieve this, a technique of dividing the metal back (i.e., an anode electrode) has been known. Here, it should be noted that such metal back division roughly includes primary division that the metal back is divided in one direction into plural strip-shaped metal backs and secondary division that the metal back is divided in two directions into plural island-shaped metal backs. In the secondary division, it is possible to reduce the discharge current as compared with the primary division.
In the case where the metal back is divided, it is necessary to secure a route for a beam current so as to suppress luminance deterioration within an acceptable level, and it is also necessary to prevent the discharge which is generated due to a potential difference at the gap formed by the division. In this connection, Japanese Patent Application Laid-Open No. 2006-173094 (corresponding to United States Patent Application Publication US2006/0103294) discloses the constitution in which a resistor is provided between divided metal backs.
However, even in the technique disclosed in Japanese Patent Application Laid-Open No. 2006-173094, further improvement is requested in regard to increase of the luminance, increase of the image quality, suppression of generation of the discharge, and suppression of the scale of the generated discharge.